Authorities Friday said 60 people were injured, five of them critically, though none of the injuries were life-threatening. The National Transportation Safety Board immediately dispatched a team to investigate the derailment. As of Monday, May 20, one person was still listed in critical condition.

The accident occurred at 6:10 p.m. near Fairfield, Conn. (about 50 miles east of New York), on a four-track segment of the Northeast Corridor just east of Metro-North’s Fairfield Metro Station, on the Bridgeport-Fairfield border. Two of the four tracks had been out of service for catenary maintenance. Amtrak immediately canceled all NEC New York-Boston service; Metro-North suspended service between South Norwalk and Bridgeport.

The outbound train, No. 1548, had left Grand Central Terminal at 4:41 p.m., bound for New Haven. When it derailed, it leaned to the left, striking the westbound train, No. 1581, which had left New Haven at 5:30 p.m. and was scheduled to arrive at Grand Central at 7:18 p.m. Seven out of eight cars on the eastbound train derailed, as well as the first car on the westbound train. Both trains remained upright.

The accident, which resulted in significant track and equipment damage, was the most serious on Metro-North since 1988, when an engineer was killed after his train, which was operating empty, crashed into another in Mount Vernon, N.Y.

In a statement Sunday, May 19, Metro-North President Howard Permut said, “Our crews will essentially be rebuilding two thousand feet of damaged track, and overhead wires and signal system,” adding, “This amounts to the wholesale reconstruction of a two-track electrified railroad. It will take multiple days of around-the-clock work to do that, and then to inspect, test and requalify the newly rebuilt infrastructure. Unfortunately, service disruptions on this section of the New Haven Line are expected to continue well into the coming week.”

Metro-North also noted that "approximately 30,000 Metro-North customers use the stations where service has been curtailed. About 125,000 use the New Haven Line as a whole, and its three branches."

Press reports during the weekend focused on overall ridership numbers without distinguishing ridership origin/destination differences, a difference that afforded some Metro-North riders normal service Monday morning. Metro-North Monday emphasized that normal service was in place between Stamford, Conn., and Grand Central Terminal, as well as on the New Canaan, Danbury, and Waterbury branches.

Shuttle train service was established Monday east of the accident site between New Haven and Bridgeport, with two shuttle bus routes providing bridge service to and from Westport, Fairfield, Fairfield Metro, and Bridgeport stations. Metro-North said its Harlem Line trains would honor New Haven Line tickets and passes, and also noted the railroad would cross-honor Amtrak tickets.

Amtrak resumed limited service Sunday, May 19, between Boston and New Haven.